Heat Transfer Enhancement in a Gas-Cooled Condenser Using Carbon Foams

摘要

Significant heat transfer enhancement by using carbon foam in the cold head of a cryocooler for liquefaction of cryogens is demonstrated. The development of an effective, lightweight and compact cold head for liquefaction of gaseous hydrogen and its subsequent densification to subcooled liquid hydrogen will require a condenser with high heat transfer coefficient and low pressure drop on the gas side. High-thermal-conductivity carbon foam is used to enhance the heat transfer coefficient. For convenience, as a first effort, this work uses air and vapor/liquid FC-87 to simulate helium and gaseous/liquid hydrogen, respectively. Experiments are conducted on carbon block foam and an alternative flow configuration called "corrugated" carbon foam, which has a lower flow resistance. Results of these experiments show that, compared with block carbon foam, corrugated carbon foam has a much lower pressure drop and a significant improvement in heat transfer performance. Experimental results of air and vapor/liquid FC-87 show that carbon-foam-based heat sinks can be 18 times better than conventional air-channel heat sinks at low speed (1 m/s).